Rhino AS-84 Door Stop Alarm 120dB (Multi Function): Can be used as a door stop alarm and door stopper even if it's turned off, rubber sole can prevent the door from opening to stop intruders. Great for in home and travel and dorm rooms. (3 Levels of Sensitivities): High,Medium & Low Sensitivities. (120db alarm): Super loud! Weight: 4.5 oz. (Powered by 9V Battery): Powered by 9V battery (not included), One piece can run for a year under normal circumstances. (Easy to Use): NO installation required, Simply place the alarm behind any door (home, hotel, college dorm room).